danger in overfilling boiler?

heinz57

what is the danger of adding water above the halfway mark in the sight glass? Will too much boiling steam in too small a space create pressure?



By way of background: I replaced my snowman looking ancient boiler in my 1920's NewEngland house shortly after moving in because the asbestos around my kids scared me. I have a nice Burnham model now but I admit to just recently paying attention to it. The reason it's grabbed my attention is

1) having to add water at least once a week (had this condition w/ former boiler. I lazily thought replacing the boiler would fix this) and

2) I noticed the air vent on the main shooting out water.



I realize that 1 & 2 are related. I've ordered a Gorton D after lurking here for a bit (right now I only have a 1/8" opening) to replace the leaky, rusty Vent Rite #1 on the main. Hopefully, w/ a bit of Blaster I can get the bushing off and get a larger pipe opening for a bigger air vent.



Anyway back to my original question. Sometimes I get a bit lazy and figure since I'm adding water, why not add a bit more so I don't have to check so often. Only after reading this site that I realize there could be a downside to that. Is there one?

Jamie Hall

Provided the water level

is somewhere between a quarter full and three quarters full in the sight glass, there shouldn't be a problem.  If the boiler is really piped right, it can be even a bit higher without problems.



The risk isn't pressure, it's carrying water over into the header and possibly into the steam mains, which leads to water hammer.



If the main vent is shooting out water, though, you may have some other problem -- it really shouldn't do that.  First thing there to check is the pressure -- it shouldn't be above 2 psi in any residential system.  1.5 is better, and many vapour systems operate best at somewhere around half a pound.

heinz57

water shooting out

Thx for putting that fear to rest. I hear hissing from radiators (recently replaced rad vents w/ Vent-Rite #1s and cleaned others w/ vinegar thx to this website) but have never heard any hammering.



And yes, the water shooting out is a concern. Until the Gorton arrives I've put in a cleaned Vent Rite and I'm keeping an eye out on the floor for water. (Water only shoots out when I raise the thermostat in the morning and I'm not always watching).



But when I got home this morning just as I heard the boiler click off I noticed it was above 3 psi (admittedly on the 0 - 30 psi gauge that came w/ the boiler).



Does the trapped air from insufficient air venting lead to higher back pressure?

Jamie Hall

No, it doesn't --

but inadequate venting will lead to reaching the cutout pressure faster, possibly causing short cycling.



However...



3 psi is too high.  And if it's on that 0 to 30 gauge (which you have to have for the insurance folks) you really don't know what the pressure is.  The pressure is controlled by the pressuretrol (or vapourstat).  If that is set properly -- no higher than 2 psi for a pressuretrol cutout (1.5 is better, if you can get it to that) and the pressure is still too high, the pigtail or the opening to the boiler or the opening to the pressuretrol itself may be clogged.  (the hissing vents and water shooting out do sort of point to pressure being too high, also, by the way)